#!/usr/bin/env python
# coding=utf-8
import pretty_errors
import re

'''
正则补充练习,题外练习
参考b站视频
https://www.bilibili.com/video/av7036891?from=search&seid=13973666358734000778
'''
text = ''
file = open('poem.txt')
for line in file:
    text = text + line
file.close()

#print(text)

result=re.findall(' *([aA][a-z][a-z]) ',text)
result=set(result)
print(result)
print(len(result))